1. Field of the Invention
This invention relates primarily to cathode ray tube display systems and in particular to the interrupt system whereby peripheral devices request access to the system.
2. Description of the Prior Art
Cathode ray tube displays originally were designed having a keyboard and a video display. New applications required additional devices to be added to the system. Communications subsystems, printers and diskettes were included in the system.
These devices were connected to a logic unit in a radial fashion. The logic unit selected devices on a predetermined priority basis.
Continued expansion of applications requirements resulted in many more devices being added to the system. The case of the microprocessor improved the throughput to make such systems feasible. However, the techniques of the Honeywell 7760 interrupt method were no longer able to provide the desired throughput. If such a system were designed to connect to a large number of devices, systems with a few devices would have considerable extra overhead logic not required for the system.